What genetic drivers control the longevity of a species?

A group of scientists of various universities studied the lifespan of fish. Why? Because some species have wide variations in lifespan even though they are the same family: rockfish.

And the results are so outstanding that Science Journal published it on its November 12th cover: Origins and Evolution of Extreme Lifespan in Pacific Ocean rockfishes.

Rockfishes are an excellent study object because their lifespan ranges from 11 to more than 200 years. 
But why do they have these enormous variations? Which factors influence their evolution?

Scientifics studied 88 rockfish species, performing a genomic analysis to discover the genetic differences that underlie their widely varying lifespans.

The researchers identified how the different rockfish species evolved from a common ancestor 10 million years ago, along the Pacific Ocean. One of them was the cabrilla, a Chilean species of rockfish studied by professor Juliana Vianna from the UC Chile Faculty of Agriculture and Forestry.

"I met Dr. Peter Sudmant and Dr. Rohit Kolora, lead authors, during my sabbatical at the University of California at Berkeley.  We worked in the same line of research in evolutionary biology, population, and adaptive genomics with vertebrates. With Dr. Sudmant, we exchanged ideas on research projects and genomic data analysis. I told him that I had researched the population genetics of cabrilla, one of the species in the study. Therefore, I contributed samples of the species and collaborated during the project's entire development from inception to publication," said professor Vianna.

The difference among the rockfish family lifespan was soon revealed.

Repercussions for humans

From this analysis, scientists discovered that immunity and DNA repair were related to longevity evolution. They found 137 longevity-associated gene variations, which involved three types of genes: 

• genes for repairing DNA,
• some genes that regulate insulin, which has long been known to influence lifespan,
• and genes that modulate the immune system.

"We identified genes (several new ones) associated with longevity. The genomic data provided a lot of information on the evolutionary biology and adaptive genomics that contributes to understanding the longevity process in vertebrates, including human," Vianna explained.

The study allow to better understand the human lifespan because found that longer-lived species have more immune genes (called butyrophilins) than shorter-live species. 

Scientists can now study how those same genes act in our bodies and develop slow age-related treatments.

The downsides of a long life

They were able to identify not just the genetic causes but the consequences of adaptation to extreme lifespan.

The study revealed the trade-offs for a long life: more years of life mean smaller populations.
In the rockfish case, a long life involves adaptations to living at a greater depth and growing larger. Big rockfish live longer but are a few, something also been studied in mammals.

The researchers focused on the variations that allowed rockfish to adapt to deeper depths and grow larger. They observed that when some species evolve to a short lifespan, their population sizes expand. And vice-versa.

Lots of the discoveries associated with lifespan have been identified before in different genetic studies. But always in a single animal species.

It is the first time scientists have checked the same pathways in a range of species.
That's why it is so relevant that Science magazine choose this research to cover this month's issue.

As Vianna said:
"It means that it is an outstanding paper in its findings. To be published in Science is an amazing thing, a dream. But to be on the cover is even better."